Körtner Gerhard, Geiser Fritz
Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia.
Naturwissenschaften. 2009 Apr;96(4):525-30. doi: 10.1007/s00114-008-0492-7. Epub 2008 Dec 10.
Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active individuals. In contrast, the widely held view is that daily torpor reduces energy expenditure usually by about 30%, is employed for a few hours every few days, and often occurs only under acute energetic stress. This interpretation is largely based on laboratory studies, whereas knowledge on daily torpor in the field is scant. We used temperature telemetry to quantify thermal biology and activity patterns of a small arid-zone marsupial, the stripe-faced dunnart Sminthopsis macroura (16.9 g), in the wild and to test the hypothesis that daily torpor is a crucial survival strategy of this species in winter. All individuals entered torpor daily with the exception of a single male that remained normothermic for a single day (torpor on 212 of 213 observation days, 99.5%). Torpor was employed at air temperatures (T (a)) ranging from approximately -1 degrees C to 36 degrees C. Dunnarts usually entered torpor during the night and aroused at midday with the daily increase of T (a). Torpor was on average about twice as long (mean 11.0 +/- 4.7 h, n = 8) than in captivity. Animals employed sun basking during rewarming, reduced foraging time significantly, and occasionally omitted activity for several days in sequence. Consequently, we estimate that daily torpor in this species can reduce daily energy expenditure by up to 90%. Our study shows that for wild stripe-faced dunnarts daily torpor is an essential mechanism for overcoming energetic challenges during winter and that torpor data obtained in the laboratory can substantially underestimate the ecological significance of daily torpor in the wild.
哺乳动物的冬眠平均持续约6个月，与活跃个体相比，可将能量消耗降低90%以上。相比之下，人们普遍认为每日蛰伏通常会使能量消耗降低约30%，每隔几天进行几个小时，并且通常仅在急性能量应激下发生。这种解释很大程度上基于实验室研究，而关于野外每日蛰伏的知识却很少。我们使用温度遥测技术来量化一种小型干旱地区有袋动物——条纹脸袋鼬（Sminthopsis macroura，体重16.9克）在野外的热生物学和活动模式，并检验每日蛰伏是该物种冬季关键生存策略的假设。除了一只雄性个体在一天内保持正常体温外（213个观察日中有212天处于蛰伏状态，占99.5%），所有个体每天都会进入蛰伏状态。蛰伏发生时的气温范围约为-1摄氏度至36摄氏度。条纹脸袋鼬通常在夜间进入蛰伏状态，并随着白天气温的升高在中午苏醒。蛰伏时间平均约为圈养状态下的两倍（平均11.0±4.7小时，n = 8）。动物在复温过程中会晒太阳，显著减少觅食时间，偶尔还会连续几天不活动。因此，我们估计该物种的每日蛰伏可使每日能量消耗降低多达90%。我们的研究表明，对于野生条纹脸袋鼬来说，每日蛰伏是其在冬季克服能量挑战的重要机制，而且在实验室获得的蛰伏数据可能会大幅低估每日蛰伏在野外的生态意义。
